Process for the surface treatment of metals



Aug. 27, 1929. M. FOLJRMENT PROCESS FOR THE SURFACE TREATMENT OF METALSFiled Nov. 29, 1926 50 tions.

Aug. 27, 192.9.

I i 1,126,431 PATENT oFFicE.'

UNITED STATES nnen. somma', or uns, rauen rnocnss iron 'rmi suanonmarxmor mais.

Application mei! November 89, 1986, Serial lv'e; 151,517,

Various processes are in use for roviding metal pieces or objects witha-su ace layer Y whose properties are different from those of -the metalconstitutin such pieces orvobjects.-

16 feet of the temperature, throughout the sur-V e metal and thus formsa surpossessing the desired protecting feac region of t face layerproperties.

For instance, in the cementation process, 20 the metal pieces arecovered with a hard layer of carbide of iron, in the Cowper- Colesprocess, with a zinc-iron alloy, in the calorization process with analuminium alloy, and' in the chrome treatment, with a chromium alloy.

' In accordance with the prior art, the pieces under treatment aredisposed in suitable boxes which are externally heated by suitable meansand in which the metal piece is raised to the proper temperature for theaction of the treating substance. But this method of operation occasionsan excessive wear of the boxes, thus increasing the cost of manufacture.

My invention relates to a method of heating the` pieces which consistsessentially in the use of high frequency induction currents, to bringthe said pieces to the proper temperature for the proposed diffusion.

I `may proceed for example in the following manner. The recipientcontaining the metal piece 'under treatment is surrounded by an inducingcoil 'which is supplied by a source of'current. In this manner, Foucaultcurrents will be produced in the surface portion of the metal piece bywhich such surface portion will be strongly heated, so that the treatingagent or active substance will become diffused throughout'these surfacepor- Suitable means are Aemployed to regulate the current and hence thetemperature of the pieces.

It is a well-known fact that if an iron bar or the like is placed withina conducting winding supplied with high frequency induction currents,Foucault currents will be set up and in France December 5, 1826.

in the bar, and chieiy in the surface portion, so that it can be heatedto any desired temperature as shown by the fact that the metal can bemelted and even volatilized.

It will be suilicient to thus heat the metal v`piece at the surface,since the treating substance will only act in the outer parts of thepiece. The degree of the heat can be accurately regulate by suitablycontrolling the inducing current.

As will be further stated my said method can be readily employed in allcases in which the metal is to be treated under pressure, in vacuo, orin the presence of an active body with or without an inert bod Variousembodiments of t e invention are shown by way of example in the appendeddrawings.

Fig. l is a sectional view of the apparatus.-

Fig. 2 is a modification, especially applicable to the casein which thetreating substance is a liquid.

Fi 3 is a second modification which is especia y ap licable to the casein which the treating su stance is a gas.

Fig. 4 isa third modification, especially suitable for use in cases inwhich the treatment is to be carried out in an active 'or inertatmosphere under pressure above or below atmospheric.

Fig. 5 is a fourth modification which is parlticularl applicable to thecontinuous treatment o bars, wires, tubes, bands or the like.

In the example shown in Fig. l, the gear wheels 4 are to be treated bythe cementation process. The inducing element consists of a copper tube1 having an internal water circulation, said tube being connected with aso'urce of high frequency electric current. The vessel 2 (containing)the cementation agent 5 consists of a suitable dielectric such as fusedsilica. Heat losses are reduced by the protecting cover 3.

In the modification shown in Fig. 2 the active or treating substance 9to be employed, which consists for example of zinc, aluminium or thelike, is maintained in the melted and liquid state either by inducedcurrents or by a suitable external source of heat. The inducing element6 surrounds the Vessel 7. The piece 8 under treatment is immersed in thebath 9.

The second modification shown in Fig. 3 relates to the case in which thetreating substance employed for coating purposes is employed in thegaseous state. The inducing has the owdered form and in which theoperation o diffusion takes place in a gaseous atmosphere (optionallyunder pressure) or in a vacuum. This will be the case for instance forthe chrome process, in which the desired result can be obtained eitherin an active or an inert gas, or in a yacuum. The piece under treatmentis placed within the powdered f covering substance 18 which is containedin the Vessel 16. The vessel 12 analogous to the one shown in Fig. 3, issurrounded by the inducing element 15 and is pierced with the apertures19 and 20 which are adapted to place the portion comprised between thetwo vessels in communication with a gas under pressure or with anapparatus producing a vacuum, or with an inert or active gas, accordingto requirements.

The fourth modification shown in Fig. 5

shows the arrangement employed for the continuous treatment of pieceshaving length, such as bars, bands, wire, tubes and the like. In thismethod, the bar 21 under treatment is causedto move at a slow rate andtraverses the vessel 22 containing the treating mixture 23. The inducingelement 24 surrounds the said vessel, which is provided with a stuingbox25 for the continuous exit of the bar after it has been covered. Y 4

Obviously, such arrangements are only particular examples of my saidprocess; the apparatus herein employed will allow the use of active :ortreating substances of a Very refractory nature such as platinum,vanadium,

tungsten, zirconium and like metals which require the use of hightemperature. I claim:

A process of causing a substance in a heated state to act upon thesurface portion of a metallic article in which the said article issurrounded by and in contact with said substance and producing highfrequency induction currents in said article, in such manner as toproduce generation of high heat in the surface portion of the article.

In testimony whereof I have aiiixed my signature.

MARCEL FOURMENT.

